A fuel cell stack start method is to provide in which without relying on oxidation and reduction condition of an anode, an output reduction of the fuel cell stack can be avoided.In the start method of a solid polymer type fuel cell stack that is comprised of a separator including an anode flow channel for flowing a fuel, another separator including a cathode flow channel for feeding an oxidant and electrodes and an electrolyte interposed between the separators, the method is characterized by performing successively a first step of feeding the fuel to the fuel cell stack under a condition that a cathode is covered by generated water, a second step of forming an oxide layer on the cathode, a third step of feeding the oxidant gas to the fuel cell stack and a fourth step of extracting load current from the fuel cell stack.